The invention relates generally to metal cutting, welding, and induction heating systems, and more particularly to thermal protection of components in a torch power unit.
A plasma cutting system creates plasma (e.g., high temperature ionized gas) to cut metal or other electrically conductive material. In general, an electrical arc converts a gas (e.g., compressed air) into plasma, which is sufficiently hot to melt the work piece while the pressure of the gas blows away the molten metal. The power output and flow of the gas can affect the performance of the system.
For example, portable plasma cutting systems may include various internal components, such as transistors or other electrical devices that may be susceptible to overheating. The overheating of these components may be further aggravated by the size and compactness of portable plasma cutting systems. Because portable systems are designed with portability as a primary function, components may be closer together, reducing the space available for air flow and heat dissipation. To prevent damage to these components, it may be desirable to turn off power to these components or turn off power to the entire system, if the components reach a critical temperature.
One way to monitor the temperature of these components is through the use of thermistors or other temperature sensors. However, addition of thermistors or other temperature sensors may complicate the manufacturing or assembly of the plasma cutting system. For example, such sensors must be inserted into the motor housings, transformer windings, or other heat-sensitive components. Additionally, some components, such as motor brushes, are not obtainable with embedded thermal sensors.